Wig, letting it burn in. As for the NOS Tung-Sol 6SN7 found or oval plate tubes, they were the most musical 6SN7 tubes I tried. Expensive though. They have a more delicate sound, highs have more air (more floating of images), mids are some of the best that I have heard from a 6SN7, bass is well defined maybe a little softer sounding. Top to bottom just more musical sounding, less overall stress sounding. Also better dimension of soundstage.
Happy Listening.